Some energy conversion processes, such as heat pumps, operate on a thermal head of only a few degrees so that the availability of large quantities of low grade heat in cold regions would provide a practical solution to many heating problems. In one conventional technique, a source of low-grade heat is created in a lake by using vertically disposed floating curtains defining a closed, segregated region in the lake, and by covering the region with floating insulation blocks. By directing the discharge of condenser water from a nuclear or conventional power station, for example, into the upper portion of the segregated region, relatively warm water deposited therein throughout the summertime will collect within the curtain and beneath the insulation blocks providing a large volume of hot water which can be maintained through the winter in northern countries such as Sweden, the insulating blocks serving to reduce conductive and radiant heat loss to the ambient environment.
A basic deficiency in the this approach, in addition to constructional and material problems, is the need to establish a segregated heat storage region in a body of water at a location adjacent a man-made source of low-grade heat. This is not always practical; and for this reason, it is an object of the present invention to provide a new and improved method of and means for seasonally storing heat in a body of water without erecting a segregated region in a body of water and without requiring a segregated region covered by floating insulating blocks to protect the heated water.